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    GNS3 and CPU

    Zsigmond P.Toth - CCNA, HP AIS



      I'm on the way of the preparation for the CCIE R&S exam.

      I have about 20U of Cisco equipment that are more suitable for CCNA and CCNP.


      As I don't have any serious one, I would like to purchase a laptop for GNS3 to simulate more complex networks with devices I just cannot afford.

      Having a limited budget for the project a laptop with Core i5 CPU and 4-8GB RAM seems to be a reasonable choise.


      From those who have real hands on experience with GNS3 please let me know how CPU cores, hyperthreading and L3 cache matter when choosing the apropriet hardware.


      Some background: http://en.wikipedia.org/wiki/Intel_Core_i5


      Thank in advance,


      Zsigmond P.Toth - HP AIS

        • 1. Re: GNS3 and CPU

          Hi Zsigmond


          Use BES to control GNS. it is free.


          Regards Conwyn

          • 2. Re: GNS3 and CPU

            Hi Zsigmond


            Try this link for some guidance.






            Message was edited by: ErickB KC

            • 3. Re: GNS3 and CPU

              If you can bump up to an i7 I recommend it - but quad core is a must IMHO.   Clock rate is less important than number of cores, because GNS3 is inherently a multithreaded application.  John - another member on here - bought a Core i7 laptop with a stout amount of RAM and he seems to be rather pleased with it. 


              However, I will say, with a laptop, USB hubs or a breakout switch are your only two options if you ever want to connect to physical switches. 

              • 4. Re: GNS3 and CPU

                Definitely agree with Travis. The number of cores is going to matter significantly. I purchased a cheap dual core laptop a while back, and although I tweaked it for several hours, there is significant difference in performance when running  GNS3 as compared to my i7. Although, I still can run about 6-8 routers, but config changes and convergence push the cpu to its max.


                In my personal opinion, the money it will cost you to get the increase may not be worth it if you are not going to use the laptop for anything else, and as Travis pointed out the limited options for connecting to physical switches. You may be able to build a solid desktop for less money.

                • 5. Re: GNS3 and CPU
                  Zsigmond P.Toth - CCNA, HP AIS

                  Thank you for all!


                  Checking the link provided and considering suggestions about cores I think I'll use GNS3 for more compex but mini lab simulations.

                  If a rack rental could not be avoided, than let it be. Bandwith is rather fine here in Budapest.

                  I also won't stop browsing eBay and friends for jackpot sales ;-)



                  Zsigmond P.Toth - HP AIS

                  • 6. Re: GNS3 and CPU

                    I personally use Amazon's EC2 running in hypervisor mode to do the heavy lifting when the topologies get big.  It's really cheap per hour.

                    • 7. Re: GNS3 and CPU

                      i'm using external hypervisor but with i3 , 2GB ram / ubuntu 10.10 i'm able to run around 9 routers (3700 Routers +  IDLE PC manipulation). there is no performance drop. I ran the INE vol1 lab in two pcs without any issues.

                      • 8. Re: GNS3 and CPU

                        Core i5 CPU and 4-8GB - Yes for CCNP; NO for CCIE;

                        unless you have external switches connected to laptop;


                        More RAM the better; i5 is not really 4 cores, 2 + 2 HT; 

                        • 9. Re: GNS3 and CPU

                          what do you mean by "external hypervisor"

                          • 10. Re: GNS3 and CPU

                            Yes for CCIE without switches we can't simulate the actual lab, but INE vol 1 & 2 have the dynamips lab configuration.


                            External hypervisor mean,  balancing the topology / router load with 2 or more PCs. I prefer to run GNS3 on Linux flavor I felt the dynamips performance is better in linux.  I think this tutorial will help 

                            How to run multi-pc topology using distributed hypervisors in GNS3

                            • 11. Re: GNS3 and CPU

                              Hi Trony,


                              Would it please be possible to post more info on using Amazon EC2 for hypervisor, What OS do you use etc?

                              Any information you have would be appreciated.

                              and I thank you for your time.

                              • 12. Re: GNS3 and CPU

                                Hi Emmanuel,


                                Well, using external hypervisors is interesting, but not truly cost effective when thinking about purchasing a laptop specifically for running GNS3. If you are going to build a machine to run GNS3 (or purchase a laptop in this case), why build one that can't handle what your looking to do.


                                If you are going to use spare PCs to balance the load, I guess that's fine if you already have them, but to build spare machines just to load balance is a bit of a waste. Although, I guess if you are using extra resources from a server or beefy PC you have, and just want a cheap laptop for messing around with other things, and use it for the occasional GNS3 lab, then I guess I understand.


                                Although, what about mobile usage away from home? What if you want to take your 10+ router lab on the road with you? Your low end laptop might not be sufficient. My job provides me with an i7 laptop, so I use it for GNS3 on occasion, but mostly when I'm on the road or going on trips with my family, I take my own laptop and the difference is quite noticeable. Maybe 4 - 6 routers on my dual core, compared to 10+ on the i7 work laptop, but if I was really trying to hammer out some labs and I was on the road, I would take the work laptop or VPN into my home machine that I specifically built for GNS3.


                                The thing is, I didn't purchase my personal laptop for GNS3, so I'm satisfied with its performance. So I'm trying to understand the purpose of purchasing a less than optimal laptop for GNS3. Its like buying a laptop for hardcore gaming, you most likely don't want a laptop that is unable to handle your favorite game, so why buy it for that purpose.


                                Just my 2 cents.


                                • 13. Re: GNS3 and CPU

                                  Martin, I run an older Core2Quad for my CCIE lab with 8GB of RAM.  I am not sure how it would stack up against the Core i5/i7 series, but it more than handles the full 9 router topology of INE connected to 4 physical switches. 

                                  • 14. Re: GNS3 and CPU
                                    Brian O'Kelly

                                    Im running my labs with an i7 on a MB Pro, works a charm. For the switching part, I convinced work to buy a few 3550s for us. You can pick em up on ebay relatively cheap now second hand. A guy I work with was using EC2 with some automated scripts to setup the environment how he wanted it. That seemed to do the job too.

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